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Abstract

Introduction: Osteoporosis and osteopenia affect roughly 10 million and 43 million older adults, respectively, in the United States. The primary way to detect osteoporosis and osteopenia is through a bone mineral density (BMD) scan, as is often done using dual energy x-ray absorptiometry (DEXA). However, previous research shows DEXA to be unreliable when assessing BMD in individuals with lumbar scoliosis. The purpose of this study was to test the effect of spine orientation on the DEXA scanning bed on lumbar BMD measures, using a cadaver spine as a model. Methods: One female cadaver was dissected to the skeletal level. The articulating joints of the lumbar vertebrae were dissected and reattached to cause right lateral bending and a Cobb angle of 35 degrees, falling into the moderate scoliosis categorization. The cadaver spine was scanned in an identical location on the scanning bed five times each in 10 different orientations. The mean values from each position were calculated and compared across orientations through the Friedman non-parametric rank sum test, and standard error of the mean and coefficient of variation were calculated to assess reliability within each orientation. Results: Across the 10 orientations, mean BMD ranged from 0.634 and 0.965 g/cm3 (t-scores ranged from -0.7 to -3.7), and 95.6% of pairwise comparisons were statistically significantly different. However, across the five scans taken for each orientation, the standard error of the mean was ≤0.003 g/cm3 and coefficient of variation was ≤0.83%. A subanalysis with three spine orientations where the spine was moved up or down by 3 cm on the scanning bed (while maintaining orientation) had little effect on BMD (mean absolute difference ≤0.025 g/cm3). Conclusion: BMD data were highly reliable when scanned multiple times in the same orientation. However, changing spine orientation resulted in dramatic changes in BMD. Future studies should seek to identify methods to best replicate spine orientation in those with lumbar scoliosis to optimize reliability across multiple scans.

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